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Cerent's first product was the Cerent 454 (later the Cisco 15454). The Cerent 454 was a second generation SONET ADM (Add-Drop Multiplexor) that also supported TCP/IP data switching. When operating as a pure ADM, the 454 could add and drop circuits from OC-192 down to Digital Signal 1 (DS1) -- later it would support Wavelength Division Multiplexing (WDM). Unlike the ADMs that preceded it, a transport signal did not have to be terminated outside the box to switch or route the TCP/IP packets. "Data cards" could be inserted into the chassis which would terminate the circuits then switch or route the packets between those terminated circuits. This capability meant carriers no longer had to purchase two boxes (e.g. an ADM and a router) just to move TCP/IP packets around its telecom network.

Other advantages of the Cerent 454 included: smaller form factor, higher port density, greater chip integration, and lower power consumption than competitors at the time.[citation needed] The unit also was the first network element to utilize TCP/IP and a web server on its management interface meaning it could be managed over a standard TCP/IP network as opposed to a more restrictive OSI network interface which was the standard in telecom networks at the time. This decision, while initially controversial, was promoted by Chip Roberson, for two pragmatic reasons: first, a TCP/IP stack came packaged with the embedded operating system from Wind River Systems and, second, the cost to acquire, test and support an OSI stack and associated network was comparatively cost-prohibitive for a young startup.

In August 1999, the company was sold to Cisco Systems for $7.2 billion[1] and became the foundation of Cisco's Optical Transport Business Unit.[2] The Cerent 454 was rebranded the Cisco 15454 and became the fastest product (at that time) to hit the $1B annual sales rate by selling $250 million in its second quarter as a Cisco business unit.